A simple technique for investigating gut passage times in small New World primates was developed, which produced good results without any need for special housing or diet, or for the separation of monkeys from their groups. This technique, which allowed the administration of a faecal
marker, chromium oxide, to specific individuals, was used to investigate gut passage times in five species of the genera Callithrix, Saguinus, Leontopithecus and Callimico. Overall average gut passage time was 4.5 hours, and there were no species differences. Such nondisruptive
methods could help in assessing the effects of dietary changes in captive monkeys, and therefore be of considerable value in improving captive diets and hence welfare and breeding success.